A cross-sectional survey of the incidence of food allergy will be conducted and compared in allergic and non-allergic populations. Histories of adverse reactions obtained in the epidemiologic survey will be verified by double blind, cross over elimination diets. Changes in symptoms, signs and peak expiratory flow rate will be recorded by patients and physicians. To confirm the validity of food allergy history and elimination diets, selected patients with proven food induced symptoms will be entered into a double blind challenge protocol under controlled conditions. Lyophilized foods will be incorporated into opaque capsules and corresponding placebo capsules will contain powdered D-L glycine. The challenge procedure is also designed as a dose response assay of specific foods. Positive tests will be defined as symptoms, signs or laboratory changes occurring 2 hr after challenge with respective food without a corresponding reaction after the placebo challenge. Biological equivalency between provocation responses and common diagnostic tests such as skin tests, dust reactions and the radioallergosorbent test will also be evaluated. More intensive studies utilizing ovalbumin will be conducted in the GCRC. The fraction will be administered through a nasal gastric tube. Jejunal biopsies will be performed before 1,3 and 6 hr after challenge. Symptoms, signs and pulmonary function changes will be evaluated every hr for the duration of 6 hr after challenge. Pertinent laboratory tests (histamine, prostaglandins, ovalbumin binding, immune complexes and complement profile) will also be measured periodically after the challenge. The therapeutic effects of cromolyn sodium and aspirin in the prevention of adverse food reactions will be evaluated in short term double blind cross over clinical trials. The effectiveness of cromolyn sodium will also be evaluated in a long-term controlled clinical study. Collectively, these investigations will establish ground rules for the objective diagnosis of food allergy in a predominantly adult population. The value of therapeutic strategies other than food elimination will also be established by this investigation.